Thread: 350 streetable engine continued

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Here is the link to the original thread.

http://www.clubhotrod.com/forums/showthread.php?t=41777

Hey Tech.

I have purchased a comp cams H270 (PART #12-211-2) and
Comp 981 springs and have borrowed the cutter to take the guide down to .660 dia for the spring.

My question now is what valve seals do I use?

I plan on using the original retainers and locks. ( can I do this? look like it should work!) I am using the original rail rockers.
By the way, I believe these haeds are factory rebuilt heads and they have .357 dia. valve stems so I think they just put oversize valves in them at rebuild. ( I had to make a larger arbour!)
Thanks
Brad

Originally Posted by bad brad

I have purchased a comp cams H270 (PART #12-211-2) and
Comp 981 springs and have borrowed the cutter to take the guide down to 0.660" dia for the spring. My question now is what valve seals do I use?

Use a 0.530" cutter to reduce the guide further and use Viton seals is what I would do. I wouldn't install the seals until I determined that I had sufficient retainer to seal clearance with the 0.470" lift. If I measured a clearance of 0.500" retainer to seal, I'd go with it. 0.030" is all Chevrolet used with the stock arrangement (0.420"/0.450").

Originally Posted by bad brad

I plan on using the original retainers and locks.

Not a good plan in my opinion. Use the retainers that Comp designed to work with their springs. If you use 10 degree retainers and locks, you can use either a standard lock or you can use a -0.050" installed height lock that will let the valve stem tip protrude up past the retainer by another 0.050" over a standard lock. You don't know if the rail rocker is going to clear the retainer with the standard lock, so make yourself an alternate plan (Plan B). 10 degree retainer is part no 750. Standard 10 degree lock is part no 611. -0.050" 10 degree lock is part no 630. Locks are cheap. Buy both part numbers and assemble with the locks that work best on your trial assembly. With the -0.050" lock, the installed height will be shorter and the spring will be stiffer by 18 1/2 lbs. (370 lbs/inch rate spring).

One of the other members may have a better idea. Sometimes I get mired down in the mud of technology and lose sight of the goal.

Thanks Tech. Do you know where I can get those seals? I couldn't find valve seals in the summit catalog!
Thanks again
Brad

Originally Posted by bad brad

Thanks Tech. Do you know where I can get those seals? I couldn't find valve seals in the summit catalog!
Thanks again
Brad

Never having used oversized-stem valves in my life, I went looking for some oversized positive seals for the intakes for you but came up empty. Standard I.D. positive seals will tolerate up to about 0.005" oversize, but +0.015" valves won't work with standard seals. Unless someone else comes up with a different plan, you may have to use umbrellas on both intake and exhaust. What are the guys at the head shop where you purchased the heads using for valve seals? Can they source a +0.015" positive seal?

there many that sell a viton seals 531x357 ? engine rebuilder and there is a guy on ebay that sells them at a very good price should look at mm size

i can get them in PEP see if a machine shop near you will get them for you the nylon/viton is #50372 342 x.630 and come 015 over size #352552 352x552 is a isuzu

New question. After assembly, my piston to deck height is average .030 down in the cylinders. To acheive the .040 clearance you were talking about Tech, I was going to use a .010 steel head gasket to keep the compression ratio you were talking about. I am not going to deck the block! What do you think?
Thanks
Brad

Originally Posted by bad brad

I am not going to deck the block!

Suit yourself.

Will keeping the clearance at .040 work similar as decking the block? I know its not the same but will it be close?